Cookies on the NHS website
We've put some small files called cookies on your device to make our site work.
We'd also like to use analytics cookies. These send information about how our site is used to services called Adobe Analytics, Hotjar and Google Analytics. We use this information to improve our site.
Let us know if this is OK. We'll use a cookie to save your choice. You can read more about our cookies before you choose.
I'm OK with analytics cookies Do not use analytics cookies
Search the NHS website
Search
My account
Health A-Z
Live Well
Mental health
Care and support
Pregnancy
Browse
More
Home Health A to Z
Overview
-
Obesity
Contents
Overview
Causes
Diagnosis
Treatment
The term obese describes a person who's very overweight, with a lot of body fat.
It's a common problem in the UK that's estimated to affect around 1 in every 4 adults and around 1 in every 5 children aged 10 to 11.
How to tell if you're obese
The most widely used method to check if you're a healthy weight is body mass index (BMI).
BMI is a measure of whether you're a healthy weight for your height. You can use the NHS BMI healthy weight calculator to work out your score.
For most adults, a BMI of:
18.5 to 24.9 means you're a healthy weight
25 to 29.9 means you're overweight
30 to 39.9 means you're obese
40 or above means you're severely obese
BMI is not used to diagnose obesity because people who are very muscular can have a high BMI without much fat.
But for most people, BMI is a useful indication of whether they're a healthy weight.
A better measure of excess fat is waist size, which can be used as an additional measure in people who are overweight (with a BMI of 25 to 29.9) or moderately obese (with a BMI of 30 to 34.9).
Generally, men with a waist size of 94cm or more and women with a waist size of 80cm or more are more likely to develop obesity-related health problems.
Risks of obesity
It's very important to take steps to tackle obesity because, as well as causing obvious physical changes, it can lead to a number of serious and potentially life-threatening conditions.
These include:
type 2 diabetes
coronary heart disease
some types of cancer, such as breast cancer and bowel cancer
stroke
Obesity can also affect your quality of life and lead to psychological problems, such as depression and low self-esteem.
Causes of obesity
Obesity is generally caused by consuming more calories, particularly those in fatty and sugary foods, than you burn off through physical activity. The excess energy is stored by the body as fat.
Obesity is an increasingly common problem because for many people modern living involves eating excessive amounts of cheap high-calorie food and spending a lot of time sitting down at desks, on sofas or in cars.
Find out why sitting too much is bad for your health
There are also some underlying health conditions that can occasionally contribute to weight gain, such as an underactive thyroid gland (hypothyroidism), although these types of conditions do not usually cause weight problems if they're effectively controlled with medicines.
Treating obesity
The best way to treat obesity is to eat a healthy reduced-calorie diet and exercise regularly.
To do this, you should:
eat a balanced calorie-controlled diet as recommended by a GP or weight loss management health professional (such as a dietitian)
join a local weight loss group
take up activities such as fast walking, jogging, swimming or tennis for 150 to 300 minutes (2.5 to 5 hours) a week
eat slowly and avoid situations where you know you could be tempted to overeat
You may also benefit from receiving psychological support from a trained healthcare professional to help change the way you think about food and eating.
If lifestyle changes alone do not help you lose weight, a medicine called orlistat may be recommended.
If taken correctly, this medicine works by reducing the amount of fat you absorb during digestion. Your GP will know whether orlistat is suitable for you.
In some cases, weight loss surgery may be recommended.
Other obesity-related problems
Obesity can cause a number of further problems, including difficulties with daily activities and serious health conditions.
Day-to-day problems related to obesity include:
breathlessness
increased sweating
snoring
difficulty doing physical activity
often feeling very tired
joint and back pain
low confidence and self-esteem
feeling isolated
The psychological problems associated with being obese can also affect your relationships with family and friends, and may lead to depression.
Serious health conditions
Being obese can also increase your risk of developing many potentially serious health conditions, including:
type 2 diabetes 
high blood pressure
high cholesterol and atherosclerosis (where fatty deposits narrow your arteries), which can lead to coronary heart disease and stroke
asthma
metabolic syndrome, a combination of diabetes, high blood pressure and obesity
several types of cancer, including bowel cancer, breast cancer and womb cancer
gastro-oesophageal reflux disease (GORD), where stomach acid leaks out of the stomach and into the gullet
gallstones 
reduced fertility
osteoarthritis, a condition involving pain and stiffness in your joints
sleep apnoea, a condition that causes interrupted breathing during sleep, which can lead to daytime sleepiness with an increased risk of road traffic accidents, as well as a greater risk of diabetes, high blood pressure and heart disease
liver disease and kidney disease
pregnancy complications, such as gestational diabetes or pre-eclampsia, when a woman experiences a potentially dangerous rise in blood pressure during pregnancy
Obesity reduces life expectancy by an average of 3 to 10 years, depending on how severe it is.
It's estimated that obesity and being overweight contribute to at least 1 in every 13 deaths in Europe.
Outlook
There's no quick fix for obesity. Weight loss programmes take time and commitment, and work best when fully completed.
The healthcare professionals involved with your care should provide encouragement and advice about how to maintain the weight loss achieved.
Regularly monitoring your weight, setting realistic goals, and involving your friends and family with your attempts to lose weight can also help.
Remember that even losing what seems like a small amount of weight, such as 3% or more of your original body weight, and maintaining this for life, can significantly reduce your risk of developing obesity-related complications like diabetes and heart disease.
Information:
Social care and support guide
If you:
need help with day-to-day living because of illness or disability
care for someone regularly because they're ill, elderly or disabled (including family members)
Our guide to care and support explains your options and where you can get support.
Couch to 5K
If it's been a long time since you did any exercise, you should check out the Couch to 5K running plan.
It consists of podcasts delivered over the course of 9 weeks and has been specifically designed for absolute beginners.
To begin with, you start running for short periods of time, and as the plan progresses, gradually increase the amount.
At the end of the 9 weeks, you should be able to run for 30 minutes non-stop, which for most people is around 5 kilometres (3.1 miles).
Page last reviewed: 16 May 2019
Next review due: 16 May 2022
Next
:
Causes
Support links
Home
Health A to Z
Live Well
Mental health
Care and support
Pregnancy
NHS services
Coronavirus (COVID-19)
NHS App
Find my NHS number
Your health records
About the NHS
Healthcare abroad
Contact us
Other NHS websites
Profile editor login
About us
Accessibility statement
Our policies
Cookies
© Crown copyright